Jet and tune
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Thread: Jet and tune

  1. #1
    Junior Member Rep728's Avatar
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    Jet and tune

    Hey new guy here. Bought a 86 trx250 need some help tuning this bike falls flat on its face from start through the gears. Took the pj carb apart and found a 152 main and 48 pilot. Compression is good. Cold starts after many kicks and choke on, once warmed up starts first second kick. Bike has a esr Intake and cool head and fmf exhaust. My question is do I need to go up or down on the jets? Plug is new did some runs and is black and wet so I know it's rich.just ordered a set of reeds as well old ones were cracked. I ride in California mostly Pismo dunes or desert

    Thanks

  2. #2
    Senior Member american opel's Avatar
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    cracked reeds will make then rich.replace them,and go with a bigger main then go from there

  3. #3
    Junior Member Rep728's Avatar
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    Looks like the piston is cracked as well dang it
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  5. #4
    Senior Member american opel's Avatar
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    sucks.time to pull it apart and go through it.

  6. #5
    Senior Member acecarlos's Avatar
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    You got lucky .....that piston is the OEM original or a cast OEM at a >66 MM.....it is ready to let go. Replace, bore, hone and chamfer all ports to the next bore size.

    Carlos


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  7. #6
    Junior Member Rep728's Avatar
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    Yah got the cylinder off today piston reads .50 on top of it was definitely cracked. Taking it to a local shop tommorow to get a new piston examine the cylinder. Hoping to get it going before Memorial Day or else I ain't got nothing to ride
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    Last edited by Rep728; 05-18-2017 at 11:44 PM.

  8. #7
    Senior Member McGruber's Avatar
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    I say just go through it all this one time and be done with it. Tear apart the carb, clean it all out. Replace any old intake boots with new ones. New fuel line. New reeds. Maybe new air filter if it needs it. Try to eliminate all possible air leaks and then see how it runs.

  9. #8
    Junior Member Rep728's Avatar
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    Quote Originally Posted by McGruber View Post
    I say just go through it all this one time and be done with it. Tear apart the carb, clean it all out. Replace any old intake boots with new ones. New fuel line. New reeds. Maybe new air filter if it needs it. Try to eliminate all possible air leaks and then see how it runs.
    Yup that's what I'm doing I cleaned the carb new line, new reeds, replacing o rings on the exhaust flange. New radiator hoses as well. Old coolant was nasty brown.


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  10. #9
    Junior Member Rep728's Avatar
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    Got my top end all back on and bike running again last night. Fired on the second kick. Local cycle shop had to bore to .60 sounds good and don't have any leaks. I also upgraded the reeds to the vforce 3. Now I will start to mess with the jetting. Carb currently has 3rd clip on needle. 152 main with a 48 pilot gonna get some fresh plugs today and see how it looks Click image for larger version. 

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  11. #10
    Senior Member american opel's Avatar
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    for any fresh builds I always use a larger main.165-175.better safe than sorry.also plug gap at .018-.020.cleaning a plug or replaceing is $2.not worth a piston and bore imo.


 
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